A paging procedure in a mobile communication system is needed when a network calls a user equipment (UE) or a plurality of UEs. Paging Type 1 and Paging Type 2 messages are used in the Universal Mobile Telecommunications System (UMTS).
The Paging Type 1 message is used when a UE is an idle mode, a Cell_PCH or a URA_PCH. A core network (CN) calls a UE in an idle mode for establishing a signaling connection or requesting an establishment of a call or session with the UE. A UE in a Cell_PCH or URA_PCH can be paged to execute a cell update or URA (UTRAN Registration Area) update procedure. In addition, the Paging Type 1 message can be used for the UTRAN to request a UE to read updated system information. All UEs in a cell are paged since the updated system information is important for the all UEs. A UE identity is included in a paging message for identifying a UE, which is high level UE identity such as an IMSI (International Mobile Subscriber Identity), TMSI (Temporary Mobile Subscriber Identity) or P-TMSI (Packet Temporary Mobile Subscriber Identity) for a UE in an idle state and which is a U-RNTI (UTRAN Radio Network Temporary Identifier) for a UE in a connected mode.
The Paging Type 2 message is used when a UE in the Cell_DCH or Cell FACH is additionally paged via a pre-established RRC connection. A dedicated paging for a specific UE is possible because the pre-established RRC connection is used.
The paging message is paired with paging indication (PI) to be transmitted on a transport channel PCH (paging channel). When a UE is paged, the UTRAN transmits the paging indication to the UE on a paging indication channel (PICH) to inform the UE that a paging message will be transmitted. The UE may receive the paging message on the PCH when a pre-determined period is elapsed after receiving the paging indication.
In the related art, radio resources for transmitting the paging message are fixed. For example, the paging indication is transmitted on a PICH having a spreading factor (SF) of 256 and the PCH including a paging message is transmitted on a S-CCPCH in the UMTS. When the paging message is transmitted through the fixed radio resources, the network cannot have flexibility for scheduling of data transmission so that it becomes hard to be applicable to the change of radio environment. Further, when a UE located in a cell boundary is paged, a paging procedure is not able to be smoothly performed since reception errors increases as a distance between the UE and an eNB is getting larger.